An Asteroid that Visited US From Interstellar Space is One of the Most Elongated Cosmic Objects Known to Science

An asteroid that visited us from interstellar space is one of the most elongated cosmic objects known to science, a study has shown, reported BBC.

Discovered on 19 October, the object's speed and trajectory strongly suggested it originated in a planetary system around another star.

Astronomers have been scrambling to observe the unique space rock, known as 'Oumuamua, before it fades from view.

Their results so far suggest it is at least 10 times longer than it is wide.

That ratio is more extreme than that of any asteroid or comet ever observed in our Solar System.

Using observations from the Very Large Telescope in Chile, Karen Meech, from the Institute for Astronomy in Honolulu, Hawaii, and colleagues determined that the object was about 400m long, rapidly rotating and subject to dramatic changes in brightness.

These changes in brightness were the clue to 'Oumuamua's bizarre shape.

"Looking at the asteroid light curve database, there are five objects (out of 20,000) that have light curves that would suggest a shape up to an axis ratio of about 7-8 to 1," Dr Meech told BBC News.

"Our errors are very small, so we are confident this is really elongated. Also, one has to realise we don't know where the rotation pole is pointed. We assumed that it was perpendicular to the line of sight. If it were tipped over at all, then there are projection effects and the 10:1 is a minimum. It could be more elongated!"

But in other respects, 'Oumuamua (pronounced oh MOO-uh MOO-uh), appears to resemble objects we know from closer to home.

"We also found that it had a reddish colour, similar to objects in the outer Solar System, and confirmed that it is completely inert, without the faintest hint of dust around it," Dr Meech said.

These properties suggest that 'Oumuamua is dense, comprised of rock and possibly metals, has no water or ice, and that its surface was reddened due to the effects of irradiation from cosmic rays over long periods of time.

Although 'Oumuamua formed around another star, scientists think it could have been wandering through the Milky Way, unattached to any star system, for hundreds of millions of years before its chance encounter with our Solar System.

"For decades we've theorised that such interstellar objects are out there, and now - for the first time - we have direct evidence they exist," said Thomas Zurbuchen, associate administrator for Nasa's science mission directorate in Washington DC.

If planets form around other stars the same way they did in the Solar System, many objects the size of 'Oumuamua should get slung out into space. The interstellar visitor may provide the first evidence of that process.

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